Swift 3 cast UITexField to Int

I'm receiving a compiler error and i'm not really sure why. I'm sure there is a simple answer for this. I have a core data attribute I'm trying to assign before saving. In my Core Data Property file it's defined as this:

@NSManaged public var age: Int32

I am using a UIPicker to select it and put it into an inputView. That works fine, so

ageTextField: UITextField!

holds the value. As I try to assign this to the CoreData object just before saving I get the following